Articles formed of rubber or latex rubber compounds have been coated with hydrophilic polymers for the purpose of providing a hydrophilic surface to the article. The known coating treatment for such products include pre-treatments of the rubber or latex which may degrade the properties of the substrate later or rubber. Such pre-treatments include the application of halogenating agents to the elastomer substrate to improve the bonding of the coating to the elastomer substrate.
An aim of this invention has been the development of an improved process for the coating of a flexible vulcanized rubber article, such as a surgeon's glove, by forming a lamination of a hydrophilic polymer, so that the external lamination of the coating of the polymer will eliminate the need for lubricating powder on the glove. Such surgeon's gloves are normally fabricated by vulcanizing, under heat, a latex rubber compound which has been applied on a ceramic mandrel with subsequent removal of the vulcanized glove from the mandrel or mold. The vulcanized latex rubber of conventional surgeon's glove may be stretched to approximately 700% of its normal length before elastic failure under tension and such flexibility is highly desired.
An important aspect of the process of the invention lies in the prevention of degradation of the elastomer substrate by control of the time of dipping of the glove in the acid solution and or the control of the temperature of the acid solution. It has been found that a typical surgeon's glove will lose a high degree of flexibility, if it is immersed in a concentrated solution of acid such as sulphuric acid for as much as a period of ten seconds or more, where the acid is at an ambient temperature of 17.degree. C. to 23.degree. C. As described hereinafter, we have limited the total elapsed time of our process, from initial starting to dip the glove in the sulfuric acid solution to final immersion in a water rinse solution, to less than ten seconds. Such gloves, when dipped in the concentrated acid at the ambient temperature described will be noticeably stiffer than an untreated glove, but will sufficiently flexible for normal use. However, we have eliminated any noticeable stiffening of the treated elastomer when we have lowered the temperature of the sulphuric acid to below 0.degree. C. and limited the total immersion time in the cooled acid to less than ten seconds. Test samples of surgeons' gloves examined ten months after processing have shown that there has been no loss of elasticity or tensile strength during that period of time after treatment with the concentrated sulfuric acid solution as described above.